Device for fixing a tube member

ABSTRACT

A device for fixing a tube member in a cavity of a patient. The device includes a body that surrounds the tube member and has a casing that at least partly forms an inner space. The body is expandable by supplying a fluid to the inner space in such a way that the fluid in the inner space has a working pressure. Furthermore, the body has, in a non-expanded state, a relatively small outer extent, which permits the introduction into said cavity, and in an expanded state, a relatively large outer extend, which permits fixing in said cavity by abutment with a contact pressure against a tubular wall of the cavity. In order to ensure a tight abutment against the wall of the cavity, the body has such a geometrical shape that the contact pressure is substantially constant independent of variations of the working pressure within a normal working range.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Swedish patent application0003420-7and is the national phase under 35 U.S.C. § 371 ofPCT/SE01/07891.

THE BACKGROUND OF THE INVENTION AND PRIOR ART

The present invention refers to a device for fixing a tube member in acavity of a patient.

By such tube members, it is in the present application referred to alltypes of pipes, which are intended to be introduced into a patient, i.e.a human being or an animal. It may for instance be so-calledendotracheal tubes, which are intended to be introduced into thetrachea, corresponding tubes for the introduction into the gullet,different types of hoses, cannulae, catheters etc. for various cavitiesof the patient.

Frequently, it is desirable to fix such hoses or tube members in thecavities of the body of the patient in order to enable introductionand/or discharge of different fluids, i.e. liquids or gases. In thatconnection, the hose is to seal against an organic surface, which in itsstructure may be irregular as well as resilient. In order to obtain sucha tight fixing, various types of fixing members are used. There arelarge requirements on such fixing members, in particular if the tubemember also is subjected to an axial movement, bending movement, turningmovement, rotation and/or if the diameter of the cavity is varying overthe time, for instance by pulsation.

The organic contact surface of the cavity, against which the fixingmember is to seal, consists of living material, which means that theblood supply to the surrounding tissue must not be hindered. Such anobstruction, which may appear if the contact pressure of the fixingmember is too large, may rapidly result in serious consequences throughthe focal death of tissue.

It is known today to use inflatable balloons as fixing members, which inthe inflated state are to be pressed against the wall of the cavity, andin such a way fix the tube member in the cavity and at the same time toprovide a proper sealing. The inflatable balloons used today areconnected with problems with regard to leakage as well as tissueinjuries.

Such leakage may be very serious, for instance in connection with arespirator treatment with the use of the endotracheal tube mentionedabove. If leakage arises, contaminated secretion from the upper airwaysmay leak bypassing the balloon down to the sterile lungs and causepneumonia. During such treatment, pressure injuries on the tissue of themucous membrane are also frequently present when using such balloons.

The rubber/plastic materials, which have thin walls and which are usedin the casings of the fixing members are permeable. Consequently, it isdifficult to maintain a consistent working pressure in the balloon. Gasis diffusing outwardly, which decreases the pressure and increases therisk of leakage. The relation is opposite when using certain anaestheticgases, which contain nitrogen oxide, wherein the gas is flowing in anopposite direction and the working pressure within the balloon increasessuccessively with a following risk of pressure injuries on the tissue.

Such a conventional balloon, seen in a longitudinal sectional view, hasa shape, which is circular, oblong or oval. It means that a changedworking pressure within the balloon gives a corresponding change of theexternal contact pressure applied to the wall of the cavity.

Furthermore, these known balloons have in a freely inflated state asmallest given extent. If the inner extent of the cavity to be sealed bythe balloon is less, small axial folds are formed on the contact surfaceof the balloon. Such folds lead to leakage and may also be irritating tothe tissue. Also in case of a moderate turning movement of the balloonin relation to the wall of the cavity, fold formation can appear.

SUMMARY OF THE INVENTION

The object of the present invention is to remedy the problems mentionedabove and to provide a fixing device, which ensures a proper sealingfunction and at the same time minimises the risk of pressure injuries onthe tissue against which the fixing device is to abut.

This object is obtained by the device initially defined, which ischaracterised in that the body has, at least in the expanded state alongthe tube member, a relatively long extension in the proximity of theouter extent and a relatively short extension in the proximity of thetube member, wherein the body has such a geometrical shape that saidcontact pressure is substantially constant independent of variations ofsaid working pressure within a normal working range.

The contact pressure will, with such a design, be provided by thegeometrical or structural shape of the body rather than by the workingpressure prevailing in the inner space. This is a very importantimprovement, since the inner working pressure will vary during use ofthe fixing device depending on the problems mentioned above regardingthe diffusion of gas into and out of the inner space, the movement ofthe body in different directions in relation to the wall of the cavity,and the variation over time of the size of the cavity. The workingpressure variations, which arise due to these causes, all lie within thenormal working range. The present invention thus provides a fixingdevice, which has an improved sealing function in situations withnon-shape permanent cavities and where external movements give anunfavourable influence of forces. At the same time it is possible,thanks to the substantial constant contact pressure, to reduce the riskof pressure injuries in various organic applications.

Such a body, which expands outwardly from the tube member, has a largeflexibility and permits a tight continuous abutment at different radiiof the cavity. Thanks to the shorter inner extension, the diameter ofthe outer extent of the body may vary with substantially the samecontact pressure. Furthermore, the contact pressure may be kept constantif the working pressure increases or decreases since the length of theshort extension may vary. The shorter extension also permits the contactsurface to slope inwardly or outwardly with respect to a centre axisthrough the tube member, either with the same angle along the wholecontact surface or with different angles for different portions. Thefixing device according to the invention is thus very suitable forcavities where the wall of the cavity does not have a linear extension.

According to an embodiment of the invention, the body is, in theexpanded state, arranged to form a contact surface at the outer extent,which is arranged to abut said wall. The casing may then advantageouslyinclude at least a portion, which extends inwardly into the inner spaceand which permits an elastic displacement of the contact surface, andmore precisely outwardly, in a radial direction with regard to thecentre axis in a direction towards and away from said wall, and inaddition a certain axial extension. By such a portion, a substantiallyconstant contact pressure may thus be obtained. Advantageously, saidportion extends around the tube member.

According to a further embodiment of the invention, the contact surfacealong the tube member is longer than said short extension. By such acontact surface, which is longer than the extension of the body in theproximity of the tube member, a proper sealing against the wall of thecavity is permitted. In that connection, the contact surface mayadvantageously include a first surrounding surface portion and a secondsurrounding surface portion, wherein these surface portions areseparated from each other by a surrounding depression. By such adividing of the contact surface into two portions, the flexibility ofthe body is further increased. The one surface portion may then, forinstance, abut the cavity wall along another extension than theextension against which the other surface portion abuts. When the deviceaccording to the invention together with the tube member is introducedinto the cavity and expanded, the geometrical shape, which the bodywould have taken in a freely expanded state, will be deformed when thebody meets the resistance of the limiting wall of the cavity. However,the body will try to take back its original shape. By the design of thereduced portions, i.e. said short extension and in certain cases alsosaid depression, one may obtain a desired size of the flexionresistance. The flexion resistance is the contact pressure, which istransferred to the walls of the cavity, and it is, for a given design,relatively constant at different degrees of flexion. By the designaccording to the invention, it is rather the working pressure in theinner space, which will vary, due to external influences, without anysubstantial change of the contact pressure against the wall of thecavity. The reduced portions will also absorb the tendency to fold,which is present in such an expandable body, which means that thecontact surface will lack all fold formations.

The geometrical shape of the body also contributes to the transfer of adirect external axial force influence on the casing to the walls of thecavity in a manner contributing to an increased security againstleakage. After relief, the pressure against the wall is normalised againand such an intermittent loading and relief may in certain organicconnections give a favourable “pulsation”, which stimulates the bloodsupply to the peripheral tissue. Advantageously, the surroundingdepression is designed in such a way that it does not abut said wall inthe expanded state.

According to a further embodiment of the invention, the body includestwo body parts. Preferably, the first surface portion is included by afirst of said body parts, and the second surface portion by a second ofsaid body parts. The two body parts are, thanks to the geometric shape,elastically flexible inwardly and outwardly, and form a respectiveelastically bendable lever, which is rotatable around a point in theproximity of a centre point of the body. It is also possible, to let thetwo body parts be separated from each other, wherein they may beprovided on the tube member at a distance from each other.

According to a further embodiment of the invention, the casing ismanufactured in a flexible material. The casing may then be designed insuch a way that the length of said short extension in the expanded stateis variable dependent on the diameter of the body with regard to theexternal extent and/or the relation between said working pressure and asurrounding pressure. Advantageously, the casing is also manufactured inan elastic material. The casing may have a thickness, which issubstantially uniform, and be pre-shaped in such a way, that it at leastpartly has said geometrical shape in a rest state, i.e. in a free statewhen the inner pressure is substantially equal to the externalsurrounding pressure, and when the body is not introduced in any cavityhaving limiting walls.

According to a further embodiment of the invention, the casing is fixedto the tube member. The casing may then include a first end portion,which is fixed to the tube member, and a second end portion, which isfixed to the tube member, wherein the tube member between the two endportions forms a limitation of the inner space. It is also possible todesign the casing in such a way that it in itself completely enclosesthe inner space. In this case, the body as whole may be moved onto andalso displaced along a tube member for adjusting the position of thebody on the tube member.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is now to be explained more closely by adescription of different embodiments and with reference to the drawingsattached.

FIG. 1 discloses a partly sectional view of a device according to theinvention in an expanded free state.

FIG. 2 discloses a partly sectional view of the device in FIG. 1introduced into a cavity with a first diameter.

FIG. 3 discloses a partly sectional view of a device in FIG. 1introduced in a cavity with a second diameter.

FIG. 4 discloses a partly sectional view of the device in FIG. 1introduced into a cavity with a third diameter.

FIGS. 5–7 disclose a sectional view of the device in FIG. 1 in variousstates.

FIG. 8 discloses a view of the device introduced into a curved cavity.

FIG. 9 discloses a view of the device in FIG. 1 subjected to turningmovements.

FIG. 10 discloses a sectional view of a device according to a secondembodiment of the invention.

FIG. 11 discloses a sectional view of a device according to a thirdembodiment of the invention.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION

FIGS. 1–9 disclose an embodiment of a device for fixing a tube member 1in a cavity 2 of a patient. FIG. 1 discloses the device in a freeexpanded state, i.e. the device is not introduced into any cavity 2. Thedevice includes a body 3, which is arranged to surround the tube member1. The body 3 is hollow and includes a casing 4, which thus at leastpartly encloses an inner space 5. In the embodiment disclosed, the innerspace 5 is formed of the casing 4 and a portion of the outer surface ofthe tube member 1. It is also possible, within the scope of theinvention, to let the casing 4 enclose completely the inner space 5,wherein the body 3 is provided on the tube member 1 in such a way that apart of the casing abuts the outer surface of the tube member 1. Thecasing 4 may according to these embodiments be fixed to the tube member1, for instance by a permanent connection such as gluing, melting orshrinking, i.e. the casing 4 is tightened around the tube member 1. Thecasing 4 is flexible and manufactured in an elastic rubber-likematerial. Advantageously, the casing 4 has a thickness, which issubstantially uniform around the inner space 5.

The tube member 1 may be substantially straight as is indicated in FIGS.1–7 and 9, or have a curved extension, as is indicated in FIG. 8. Thetube member includes a centre axis x, which thus also may be straight orhave a certain curvature. The centre axis x also forms a centre axis forthe body 3. The device is disclosed in FIGS. 1–4, partly cut along thecentre axis x and in FIGS. 5–7 completely cut along the centre axis x.

The body 3 is expandable by the supply of a fluid to the inner space 5via supply conduit 6. The fluid may be a gas, a liquid or a foam. Thesupply conduit 6 is merely disclosed in Fig 1 for the sake ofsimplicity. The body 3 may thus be in a non-expanded state, wherein thefluid substantially has been sucked out of the inner space 5. The bodymay also be in an expanded state, which is disclosed in Figs 1–9,wherein the fluid has been supplied in such a way that a workingpressure prevails in the inner space 5. In the non-expanded state, thebody 3 has a relatively small radial, external extent, which permits theintroduction into the cavity 2. In the expanded state, the body 3 has arelatively large radial, external extent, which permits fixing of thebody 3 in said cavity 2 by pressing the body 3 against a tubular innerwall 7, which at least partly defines the cavity 2. The body 3 then hasa contact surface, which abuts the wall 7. In the embodiment disclosed,the body 3 has two body parts 3 aand 3 b, wherein the contact surfaceincludes two separate surface portions 8 and 9, one for each body part 3aand 3 b, which surfaces are separated from each other by a surroundingdepression or groove 10, which extends around the tube member 1 andinwardly into the inner space 5. Each body part 3 a, 3 b forms anelastically flexible lever, which is rotatable around a point at or inthe proximity of a surrounding line 0, see Fig 4.

The body 3 has such a geometrical shape and such a structure, that thecontact pressure, at which the surface portions 8 and 9 abut the wall 7,is substantially constant independent of variations of the workingpressure in the inner space 5 within a normal working range, i.e. normalvariations in the working pressure, which may lie between 10 and 30 mmHg. Such normal variations of the working pressure arise due todiffusion of gas into and out of the inner space 5, movements of thebody 3 in relation to the wall 7 of the cavity 2 and normal sizevariations of the cavity 2 over the time. The geometrical shape of thebody 3 is thus structurally determined or pre-shaped in connection withthe manufacture of the device. The body 3 will thus have this pre-shapedgeometry in a rest state, i.e. when substantially the same pressureprevails outside the casing 4 as in the inner space 5. Also in the freestate, which is disclosed in FIG. 1, the body 3 has this pre-shapedgeometry.

As appears clearly from FIGS. 2–4, the body 3 has in the expanded statealong the tube member 1 and the centre axis x a relatively long axialextension at or in the proximity of the outer extent, cf. the line a inFIG. 2, and a relatively short axial extension at or in the proximity ofthe tube member 1, cf. the line b in FIG. 2. More precisely, the contactsurface, together with the depression 10 between the surface portions 8and 9 has a longer axial extension then than the body 3 in the proximityof the tube member 1. In such a way, a portion 11 is formed, whichextends around the tube member 1 and inwardly into the inner space 5 ofthe body 3 in the proximity of the tube member 1 when the body 3 is seenin the longitudinal section. In FIG. 2, the cavity 2 has a relativelylarge inner diameter d, i.e. a relatively large diameter betweenopposite wall surfaces of the wall 7. The shorter extension of the body3 then has a larger length than the corresponding short extension of thebody 3 when said diameter d is shorter, which appears from FIGS. 3 and 4in comparison with FIG. 2. At the same time, the length of the body 3increases at the radially outer extent when said diameter d decreases.At the same time, the depression 10 will decrease in its size when theabove mentioned diameter d decreases. Thanks to these flexion locations,i.e. the portions 11 and 10 of the body 3, the contact pressure againstthe wall 7 of the cavity 2 will be substantially equal independent ofthe length of said diameter d.

FIG. 5 discloses schematically by means of arrows the contact force indifferent positions of the surface portions 8 and 9 when the body 3 isin a normal expanded state without any substantial influence fromexternal forces.

In FIG. 6, a higher pressure prevails to the right of the device than tothe left thereof. This leads to the result that the waist to the rightof the body 3 will be pressed inwardly, which means that the contactforce against the wall 7 from the surface portion 9 increases whereasthe contact force of the surface portion 8 is more uniformlydistributed. In the same way, a somewhat smaller contact force isobtained from the surface portion 9 than from the surface portion 8 ifthe pressure is higher to the right of the device than to the leftthereof, as is disclosed in FIG. 7, i.e. the waist will be displaced tothe right and increase the contact force of the surface portion 8.

FIG. 8 illustrates how the two surface portions 8 and 9 maintain thetight abutment against the wall 7 with a substantially uniform contactforce, even if the wall 7 is slightly curved in the direction of theaxis x, at the same time as the fold formation of the surface portions 8and 9 is prevented. The folding or the fold formation takes place in thedepression 10, which is not in contact with the wall 7.

In a corresponding manner, a uniform contact pressure of the surfaceportions 8 and 9 may be maintained even if the two surface portions 8are subjected to turning forces in opposite direction at the same timeas fold formation of the surface portions 8 and 9 is prevented. Thefolding or the fold formation takes place in the depression 10, which isnot in contact with the wall 7.

FIG. 10 discloses a second modified embodiment of the invention,according to which the body 3 has a long extension directly at the tubemember 1 and a shorter extension at the line b in the proximity of thetube member 1. In the proximity of the outer extent, line a, thelongitudinal extension is longer than at the line b, but shorter thandirectly at the tube member 1. In this embodiment, the inner space 5 iscompletely enclosed by the casing. The casing 4, and thus the body 3, isconsequently displaceable on the tube member 1 in the direction of thecentre axis x.

FIG. 11 discloses a third embodiment, which differs from the first andsecond embodiments in that the body 3 includes two separate body parts 3a and 3 b, which both are attached to the tube member 1 at a distancefrom each other. Preferably, both body parts 3 a, 3 b are supplied witha fluid in such a way that substantially the same working pressureprevails in each body part 3 a, 3 b.

The invention is not limited to the embodiment disclosed but may bevaried and modified within the scope of the following claims.

1. An endotrachael tube, comprising: a tube member having a center axis;and a device operative to position the tube in a cavity of a patient,the device comprising an expandable body surrounding a portion of thetube member, the body comprising two body parts that at least partiallyenclose a single continuous inner space, each body part comprising acontact surface operative to engage a wall of the cavity in an expandedstate, each contact surface extending about the center axis, the bodyfurther comprising a depression surrounding the tube member between thetwo body parts and extending into the inner space, wherein the body isexpandable by supplying a fluid to the inner space such that the fluidin the inner space has a working pressure, wherein in an unexpandedstate the body is insertable into the cavity and in the expanded statethe contact surfaces abut the wall of the cavity, wherein in theexpanded state the body extends a greater distance in a directionparallel to the center axis of the tube member in the vicinity of thecontact surface as compared to in the vicinity of the tube member, suchthat the two body parts form respective elastically bendable levers,thereby resulting in the body exerting a substantially constant contactpressure on the wall of the cavity independent of variations in theworking pressure of the fluid within a normal working range.
 2. Theendotracheal tube according to claim 1, wherein in the expanded statethe body extends a greater distance in a direction parallel to thecenter axis of the tube member in the vicinity of the contact surfaceand in the vicinity of the tube member as compared to an intermediateregion between the contact surface and the tube member.
 3. Theendotracheal tube according to claim 1, wherein the depression does notabut the wall of the cavity with the body in an expanded state.
 4. Theendotracheal tube according to claim 1, wherein the expandable bodycomprises a flexible material.
 5. The endotracheal tube according toclaim 1, wherein in the vicinity of the tube member the body extends avariable distance in a direction parallel to the tube member dependingupon at least one of a diameter of the body, outer extent of the body,or working pressure relative to surrounding pressure.
 6. Theendotracheal tube according to claim 1, wherein the expandable bodycomprises an elastic material.
 7. The endotracheal tube according toclaim 1, wherein the expandable body has a substantially uniformthickness.
 8. The endotracheal tube according to claim 1, wherein theexpandable body is fixed to the tube member.
 9. The endotracheal tubeaccording to claim 1, wherein the expandable body comprises a firstportion that is fixed to the tube member and a second portion that isfixed to the tube member, wherein between the first portion and thesecond portion the tube member acts as a delimitation of the innerspace.
 10. The endotracheal tube according to claim 1, wherein theexpandable body is displaceably arranged on the tube member.